The present invention relates to a suspension control system for a vehicle which may suitably be used for vehicle height control, for example.
There has heretofore been one type of control system that controls the height of a vehicle by extending and contracting hydraulic cylinders associated with the wheels of the vehicle. This type of control system is activated in response to a height designating signal input by a manual operation. Alternatively, the control system automatically controls the length of each hydraulic cylinder in response to a vehicle height signal from a vehicle height sensor.
The conventional control system of the type described above suffers, however, from the following problems. For example, in a vehicle wherein the distance between the vehicle body and front wheels is controllable, charge or discharge of the hydraulic fluid Is simultaneously carried out for two cylinders associated with the two front wheels. Therefore, these two cylinders are communicated with each other through the piping for the hydraulic fluid. Accordingly, when rolling occurs, the hydraulic fluid flows from the outer cylinder to the inner cylinder, thus aggravating the rolling. If the hydraulic fluid charge-discharge operation for the two cylinders is stopped by shutting off the hydraulic communication to the cylinders in the above-described state, the cylinders are locked in a state where the vehicle body is tilted thereby.